Blade control device for work machine

ABSTRACT

In a blade control device, in a case where an update condition set in advance is satisfied, a virtual design surface setting part sets a virtual design surface, using a blade position when the update condition is satisfied as a reference, at an angle equivalent to a vehicle body angle, and a blade operation control part restricts raising and lowering operation of a blade such that the blade conducts the raising and lowering operation above the virtual design surface.

TECHNICAL FIELD

The present invention relates to a blade control device provided in awork machine including a blade.

BACKGROUND ART

Conventionally, a work machine including a blade for use in digging ofthe ground, land grading, transport of sediments, and the like has beenused widely. Although there is proposed a method of automaticallycontrolling raising and lowering operation of a blade such that a bladeload applied to the blade becomes substantially constant in such a workmachine, the method has a problem of waviness of an execution surfacegenerated due to raising and lowering operation of a blade.

Patent Literature 1 discloses a blade control device intended tosuppress waviness of an execution surface. In the blade control deviceof Patent Literature 1, while restricting fluctuation of a blade toabove a virtual design surface set in parallel to a design surface andcloser to the blade than to the design surface, a blade operationcontrol part lowers the blade in a case where a blade load is smallerthan a first set load value, and raises the blade in a case where theblade load is greater than a second set load value which is greater thanthe first set load value. A virtual design surface setting part resetsthe virtual design surface parallel to the design surface when the bladeload is lowered from a value equal to or greater than the first set loadvalue to a value smaller than the first set load value. In the bladecontrol device of Patent Literature 1, the virtual design surfacesetting part also sets a virtual design surface at a position more awayfrom the design surface than a virtual design surface set last time. Inother words, a virtual design surface will be upwardly moved more awayfrom the design surface every time the virtual design surface isupdated.

However, since in such a blade control device recited in PatentLiterature 1 as described above, in a case, for example, where a presentsurface (the ground) has an up-grade or a down-grade with respect to ahorizontal design surface and a work machine conducts digging work whileascending a slope along the present surface or descending the slopealong the present surface, a blade load is greatly affected by agradient of the present surface, raising and lowering operation of theblade is increased, so that an effect of suppressing waviness of anexecution surface cannot be always considered sufficient.

CITATION LIST Patent Literature

Patent Literature 1: JP 5285805 B

SUMMARY OF INVENTION

An object of the present invention is to provide a blade control devicewhich is provided in a work machine including a blade and controlsraising and lowering operation of the blade, the blade control devicebeing capable of effectively suppressing waviness of an executionsurface.

A blade control device of the present invention is a device which isprovided in a work machine including a machine body having a travellingdevice and a vehicle body supported by the travelling device and a bladeattached to the machine body so as to be raised and lowered and whichcontrols raising and lowering operation of the blade. The blade controldevice includes a target design surface setting part which sets a targetdesign surface that specifies a target shape of an object to be dug bythe blade; a position information acquiring part which acquires positioninformation related to the work machine; a blade position calculatingpart which calculates a blade position as a position of the blade on thebasis of the position information acquired by the position informationacquiring part; a virtual design surface setting part which sets avirtual design surface above the target design surface; and a bladeoperation control part which controls the raising and lowering operationof the blade. In a case where an update condition set in advance issatisfied, the virtual design surface setting part sets the virtualdesign surface, using the blade position when the update condition issatisfied as a reference, at an angle equivalent to a vehicle body angleas an angle of inclination of the vehicle body with respect to ahorizontal surface, the angle of inclination being obtained on the basisof the position information. The blade operation control part restrictsthe raising and lowering operation of the blade such that the bladeconducts the raising and lowering operation above the virtual designsurface.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side view showing a hydraulic excavator as an example of awork machine in which a blade control device according to an embodimentof the present invention is provided.

FIG. 2 is a block diagram showing a main function of the blade controldevice according to the embodiment.

FIG. 3 is a flowchart showing one example of control operation to beexecuted by a controller included in the blade control device.

FIG. 4 is a flowchart showing one example of control operation to beexecuted by a blade operation control part out of the control operationto be executed by the controller.

FIG. 5 is a flowchart showing one example of control operation to beexecuted by a virtual design surface setting part out of the controloperation to be executed by the controller.

FIG. 6 is a schematic side view for explaining an estimated position inthe blade control device.

FIG. 7 is a schematic side view for explaining setting of a virtualdesign surface in the blade control device.

FIG. 8 is a flowchart showing one example of control operation to beexecuted by a blade control restricting part out of the controloperation to be executed by the controller.

FIG. 9 is a schematic side view showing one example of a design surface,a present surface, a virtual design surface, and an execution surfacewhen the work machine provided with the blade control device conductsdigging work while ascending a slope along the present surface.

FIG. 10 is a schematic side view showing one example of a designsurface, a present surface, a virtual design surface, and an executionsurface when the work machine provided with the blade control deviceconducts the digging work while descending a slope along the presentsurface.

FIG. 11 is a schematic side view showing one example of a designsurface, a present surface, a virtual design surface, and an executionsurface when the work machine provided with the blade control deviceconducts the digging work while ascending and descending a slope alongthe present surface.

FIG. 12 is a block diagram showing a main function of a blade controldevice according to a modification example of the embodiment.

FIG. 13 is a flowchart showing one example of control operation to beexecuted by a controller included in the blade control device accordingto the modification example.

FIG. 14 is a schematic side view showing one example of a designsurface, a present surface, a virtual design surface, and an executionsurface when a work machine provided with the blade control deviceaccording to the modification example conducts digging work whileascending and descending a slope along a present surface.

FIG. 15 is a schematic side view showing one example of a designsurface, a present surface, a virtual design surface, and an executionsurface when a work machine provided with a blade control deviceaccording to a reference example conducts digging work while ascending aslope along a present surface.

FIG. 16 is a schematic side view showing one example of a designsurface, a present surface, a virtual design surface, and an executionsurface when the work machine provided with the blade control deviceaccording to the reference example conducts the digging work whiledescending a slope along the present surface.

DESCRIPTION OF EMBODIMENTS

A preferred embodiment of the present invention will be described withreference to the drawings.

Overall Structure of Work Machine

FIG. 1 is a side view showing a hydraulic excavator 1 as an example of awork machine in which a blade control device according to an embodimentof the present invention is provided. The hydraulic excavator 1 includesa travelling device 2 (lower travelling body) capable of travelling onthe ground G, a vehicle body 3 (upper slewing body) mounted on thetravelling device 2, a work device mounted on the vehicle body 3, and ablade 4 mounted on the travelling device 2 or the vehicle body 3. Thetravelling device 2 and the vehicle body 3 constitute a machine body ofthe work machine. The vehicle body 3 has a slewing frame, an engine, adriver's room, and the like.

The work device mounted on the vehicle body 3 includes a boom 5, an arm6, and a bucket 7. The boom 5 has a base end portion supported at afront end of the slewing frame so as to go up and down, i.e., to beturnable around a horizontal axis, and a distal end portion on theopposite side. The arm 6 has a base end portion attached to the distalend portion of the boom 5 so as to be turnable around the horizontalaxis, and a distal end portion on the opposite side. The bucket 7 isturnably attached to the distal end portion of the arm 6.

The hydraulic excavator 1 has a boom cylinder, an arm cylinder, and abucket cylinder provided for the boom 5, the arm 6, and the bucket 7,respectively. The boom cylinder is interposed between the vehicle body 3and the boom 5 and extends and contracts so as to cause the boom 5 toconduct up-down operation. The arm cylinder is interposed between theboom 5 and the arm 6 and extends and contracts so as to cause the awl 6to conduct turning operation. The bucket cylinder is interposed betweenthe arm 6 and the bucket 7 and extends and contracts so as to cause thebucket 7 to conduct turning operation.

The blade 4 mounted on the travelling device 2 or the vehicle body 3 isprovided for conducting digging of the ground, land grading, transportof sediments, and the like. Specifically, the blade 4 is supported by alift frame 4 a, and the lift frame 4 a is supported to be turnablearound a horizontal axis 4 b with respect to the travelling device 2.Accordingly, the blade 4 can be displaced in an up-down direction withrespect to the travelling device 2.

The hydraulic excavator 1 has a lift cylinder 8 provided for the blade4. The lift cylinder 8 has a head chamber 8 h and a rod chamber 8 r (seeFIG. 1), and extends to thereby cause the blade 4 to move in a downdirection when a hydraulic oil is supplied to the head chamber 8 h, aswell as discharging the hydraulic oil in the rod chamber 8 r, and alsocontracts to thereby cause the blade 4 to move in an up direction whenthe hydraulic oil is supplied to the rod chamber 8 r, as well asdischarging the hydraulic oil in the head chamber 8 h.

The hydraulic excavator 1 has a hydraulic circuit not shown. Thehydraulic circuit includes the boom cylinder, the arm cylinder, thebucket cylinder, and the lift cylinder 8. The hydraulic circuit furtherincludes a hydraulic pump 9 (see FIG. 1), a lift cylinder controlproportional valve 41 (see FIG. 2), and a lift cylinder flow ratecontrol valve not shown.

Blade Control Device

FIG. 2 is a block diagram showing a main function of a blade controldevice 100. The blade control device 100 is provided for controllingraising and lowering operation of the blade 4. The blade control device100 includes a controller 10 (mechatronic controller), a positioninformation acquiring part, a blade load acquiring part 34, an automaticcontrol switch 35, and a travelling lever 36 for manipulating thetravelling device 2. The controller 10, which is configured with, forexample, a microcomputer, controls operation of each element included inthe hydraulic circuit.

The position information acquiring part is configured to acquireposition info,. nation about the hydraulic excavator 1. Specifically, inthe present embodiment, the position information acquiring part includesa vehicle body position acquiring part 31, a vehicle body angleacquiring part 32, and a blade angle acquiring part 33. The vehicle bodyposition acquiring part 31 is configured to acquire a vehicle bodyposition as a position of the machine body. The vehicle body positionacquiring part 31 is configured with, for example, a receiver, such as aGNSS receiver (GNSS sensor), capable of receiving satellite data(positioning signal) from a satellite measurement system, such as GNSS(Global Navigation Satellite System), and receives GNSS data indicativeof a vehicle body position as a position of the vehicle body 3 in aglobal coordinate system. The global coordinate system is athree-dimensional coordinate system using an origin point defined on theearth as a reference, which is a coordinate system indicating anabsolute position defined by the satellite measurement system.

The vehicle body angle acquiring part 32 is configured to acquire avehicle body angle as an angle of the vehicle body 3. The vehicle bodyangle acquiring part 32 is configured with, for example, a vehicle bodyangle sensor which detects an angle of the vehicle body 3 in a globalcoordinate system. Specifically, the vehicle body angle sensor may beconfigured with, for example, one or a plurality of receivers providedin the machine body and capable of receiving satellite data (positioningsignal) from a satellite measurement system. The vehicle body angle isan angle of inclination of the vehicle body with respect to a horizontalsurface.

The blade angle acquiring part 33 is configured to acquire an angle ofthe blade 4. The blade angle acquiring part 33 is configured with, forexample, a blade angle sensor which detects the angle of the blade 4 ina global coordinate system. Specifically, the blade angle sensor may beconfigured with, for example, one or a plurality of receivers providedin the machine body and capable of receiving satellite data (positioningsignal) from a satellite measurement system.

A local coordinate system may be used in place of the global coordinatesystem. Both the global coordinate system and the local coordinatesystem may be used together. Examples of the local coordinate systeminclude a three-dimensional coordinate system using the vehicle bodyposition as a reference and a three-dimensional coordinate system usinga specific position at a work site as a reference. In the above case,the vehicle body angle sensor may be configured with, for example, aninertia measurement device, or may be configured with, for example, theinertia measurement device and the receiver capable of receiving thesatellite data. The inertia measurement device may be configured to becapable of, for example, measuring an acceleration and an angularvelocity of the vehicle body 3, and detecting an inclination (e.g., apitch indicative of rotation with respect to an X-axis, a yaw indicativeof rotation with respect to a Y-axis, and a roll indicative of rotationwith respect to a Z-axis) of the vehicle body 3 on the basis of ameasurement result. The blade angle sensor may be configured with, forexample, a stroke sensor which detects a cylinder stroke of the bladecylinder 8, or may be configured with the stroke sensor and the receivercapable of receiving the satellite data.

Although, in the present embodiment, the vehicle body position acquiringpart 31 and the vehicle body angle acquiring part 32 are attached to anupper portion of the vehicle body 3 and the blade angle acquiring part33 is attached to an upper portion of the blade 4 as shown in FIG. 1,the attachment positions are not limited to the specific example shownin FIG. 1. Detection signals as electrical signals generated by theseacquiring parts 31, 32, and 33 are input to the controller 10.

In the present embodiment, the blade load acquiring part 34 isconfigured to acquire a blade load as a load applied on the blade 4during digging work. The blade load corresponds to, for example, a pumppressure of the hydraulic pump 9 which drives the blade 4. Accordingly,the blade load acquiring part 34 is capable of detecting the blade loadby detecting the pump pressure. In the present embodiment, the bladeload acquiring part 34 includes a head pressure sensor 34H which detectsa head pressure P1 as a pressure of a hydraulic oil in the head chamber8 h of the lift cylinder 8, and a rod pressure sensor 34R which detectsa rod pressure P2 as a pressure of a hydraulic oil in the rod chamber 8r of the lift cylinder 8. The sensors 34H and 34R respectively converttheir detected physical quantities into detection signals as electricalsignals corresponding to the physical quantities and input the detectionsignals to the controller 10.

The automatic control switch 35 is arranged in the driver's room and iselectrically connected to the controller 10. Upon receiving manipulationfor switching a control mode of the controller 10 from a manualmanipulation mode to an automatic control mode, the automatic controlswitch 35 inputs a mode command signal related to the manipulation tothe controller 10. The controller 10 switches setting of the controlmode from the manual manipulation mode to the automatic control mode bythe mode command signal input from the automatic control switch 35.

In the automatic control mode, the controller 10 is configured toautomatically control operation of the lift cylinder 8 such that anexecution surface to be executed by the blade 4 approaches a targetdesign surface set in advance. When a command value (command current) tothe lift cylinder control proportional valve 41 for controllingoperation of the lift cylinder 8 is output from the controller 10, asecondary pressure of the proportional valve 41 changes according to thecommand value and opening of the lift cylinder flow rate control valvechanges according to the secondary pressure. As a result, a supply flowand a supply direction of a hydraulic oil to be supplied from thehydraulic pump 9 to the lift cylinder 8 via the lift cylinder flow ratecontrol valve change to control an operation speed and a drivingdirection of the lift cylinder 8. On the other hand, in the manualmanipulation mode, when a worker manipulates the travelling lever 36, amanipulation signal of the manipulation is input to the controller 10,and the command value to the lift cylinder control proportional valve 41or a command value to the lift cylinder flow rate control valve isoutput from the controller 10 according an amount of manipulation of amanipulation lever not shown for manipulating raising and lowering ofthe blade 4.

The controller 10 has a target design surface setting part 11, a bladeposition calculating part 12, a storage part 13, a virtual designsurface setting part 14, a blade operation control part 15, a loadthreshold value setting part 16, a blade control restricting part 20,and an estimated position calculating part 22 as a function forexecuting the automatic control.

The target design surface setting part 11 sets a target design surfaceSD (see FIG. 7) which specifies a target shape of an object to be dug bythe blade 4. The target design surface setting part 11 may store adesign surface input by a target design surface input part provided inthe driver's room and set the design surface as a target design surface.The target design surface setting part 11 may also store data of adesign surface acquired via various kinds of storage media, acommunication network, or the like and set the design surface as atarget design surface. The target design surface setting part 11 inputsthe set target design surface to the virtual design surface setting part14. The target design surface SD is a surface which specifies athree-dimensional design topography as a target shape of the groundwhich is an object to be dug. The target design surface SD may bespecified by external data such as BIM, CIM (Building/ConstructionInformation Modeling, Management), etc., or may be set using a positionof the work machine as a reference.

The blade position calculating part 12 calculates a blade position as aposition of the blade 4 in the global coordinate system on the basis ofthe position information acquired by the position information acquiringpart. In the present embodiment, the blade position calculating part 12calculates the blade position on the basis of the vehicle body positionacquired by the vehicle body position acquiring part 31, the vehiclebody angle acquired by the vehicle body angle acquiring part 32, and theangle of the blade 4 acquired by the blade angle acquiring part 33. Inother words, the blade position is calculated from a sum of a vectorfrom a reference point to the vehicle body position and a vector fromthe vehicle body position to the blade position. Although in the presentembodiment, a blade position is thus calculated from a relative anglebetween the vehicle body angle and the angle of the blade 4 in theglobal coordinate system, a blade position calculation method is notlimited thereto. The blade position may be calculated on the basis of,for example, a length of the lift cylinder 8, or may be calculated onthe basis of GNSS data received by a GNSS receiver (GNSS sensor)attached to the blade 4.

Although in the present embodiment, the blade position is set at a bladeedge position (a position of a lower edge of a distal end of the blade4) as the distal end of the blade 4, the blade position may be set atother part of the blade 4.

The storage part 13 stores a first load threshold value f1 as a loadthreshold value which is a threshold value of the blade load f. In thepresent embodiment, the storage part 13 further stores a second loadthreshold value f2 which is a threshold value of the blade load f. Thefirst load threshold value f1 and the second load threshold value f2will be described later.

Additionally, the storage part 13 stores an update condition set inadvance. The update condition is used as a reference for determiningwhether or not the virtual design surface setting part 14 should updatea virtual design surface to be described later. The update conditionincludes one or a plurality of conditions. The update condition will bedetailed later.

In a case where the update condition is satisfied, the virtual designsurface setting part 14 sets a virtual design surface to be above thetarget design surface using the blade position when the update conditionis satisfied as a reference, the virtual design surface being parallelto the vehicle body angle acquired by the vehicle body angle acquiringpart 32. The virtual design surface setting part 14 sets a virtualdesign surface on the basis of a blade position calculated by the bladeposition calculating part 12, the first load threshold value f1 set bythe load threshold value setting part 16, the blade load f acquired bythe blade load acquiring part 34, a vehicle body position acquired by aGNSS receiver (the vehicle body position acquiring part 31), a vehiclebody angle acquired by a vehicle body angle sensor (the vehicle bodyangle acquiring part 32), and a target design surface set by the targetdesign surface setting part 11. A specific setting method will bedescribed later.

The load threshold value setting part 16 sets a load threshold value foruse in calculation in the virtual design surface setting part 14 and theblade operation control part 15. In the present embodiment, the loadthreshold value setting part 16 sets the above-described first loadthreshold value f1 and second load threshold value f2. The second loadthreshold value f2 is set to be a value greater than the first loadthreshold value f1. The first load threshold value f1 is set to be avalue corresponding to a proper blade load f with which the hydraulicexcavator 1 can stably travel. The second load threshold value f2 is avalue set to realize stable and efficient digging operation. Because ofbeing a value set for preventing occurrence of such a situation that theblade load f becomes excessively large to cause a stuck state, thesecond load threshold value f2 is preferably set to be a value smallerthan a blade load with which such a situation occurs. In other words,even when the blade load f reaches the second load threshold value f2,the second load threshold value f2 is preferably set to be a value withwhich the work machine can travel. These load threshold values f1 and f2may be manually input to the controller 10 by a worker before thedigging work or appropriately calculated by the controller 10 and storedduring the digging work.

The blade operation control part 15 calculates and outputs a commandvalue to the lift cylinder control proportional valve 41 for controllingoperation of the lift cylinder 8. The blade operation control part 15calculates a temporary command current to be output to the lift cylindercontrol proportional valve 41 on the basis of an automatic controlswitch manipulation signal of the automatic control switch 35, atravelling lever manipulation signal of the travelling lever 36, theblade load f acquired by the blade load acquiring part 34, and the firstload threshold value f1 and the second load threshold value f2 set bythe load threshold value setting part 16. A specific calculation methodwill be described later.

The blade control restricting part 20 calculates a command current to beoutput to the lift cylinder control proportional valve 41 on the basisof a virtual design surface calculated by the virtual design surfacesetting part 14 and the temporary command current calculated by theblade operation control part 15. A specific calculation method will bedescribed later.

The estimated position calculating part 22 calculates an estimatedposition of a present surface configuring a part of conditions includedin the update condition. Specifically, the estimated positioncalculating part 22 calculates an estimated position of a part of thepresent surface which is the ground as the object to be dug, the partbeing associated with at least one of the blade 4 and the travellingdevice 2, on the basis of the position information acquired by theposition information acquiring part. A specific calculation method willbe described later.

Next, description will he made of control operation conducted by thecontroller 10 for the driving of the blade 4 in the automatic controlmode with reference to the flowchart of FIG. 3.

The controller 10 acquires an automatic control switch manipulationsignal related to the automatic control switch 35 and a travelling levermanipulation signal related to the travelling lever 36 (Step S1).

Next, the controller 10 determines whether a condition is satisfied ornot, the condition being that the automatic control switch manipulationsignal indicates that the automatic control switch 35 is in an ON stateand the travelling lever manipulation signal indicates that thetravelling lever 36 has been manipulated (Step S2). In a case where thecondition is not satisfied (NO in Step S2), the controller 10 resets avirtual design surface and finishes the processing.

In a case where the condition is satisfied (YES in Step S2), the loadthreshold value setting part 16 sets the first load threshold value f1and the second load threshold value f2 (Step S3).

Next, the blade load acquiring part 34 acquires a blade load f appliedto the blade 4 (Step S4).

Next, the blade operation control part 15 calculates the temporarycommand current (Step S5). FIG. 4 is a diagram showing a flow forcalculation of the temporary command current by the blade operationcontrol part 15 of the controller 10. As shown in FIG. 4, the bladeoperation control part 15 determines whether a condition that the bladeload f acquired by the blade load acquiring part 34 is equal to orgreater than the second load threshold value f2 is satisfied or not(Step S101). In a case where the condition is satisfied (YES in StepS101), the blade operation control part 15 outputs a temporary commandcurrent corresponding to “lift-up” and finishes the processing. Thetemporary command current is input to the blade control restricting part20. “Lift-up” corresponds to operation of raising the blade 4.

In a case where the condition of Step S101 is not satisfied (NO in StepS101), the blade operation control part 15 determines whether acondition is satisfied or not, the condition being that the blade load fis equal to or greater than the first load threshold value f1 (StepS102). In a case where the condition of Step S102 is satisfied (YES inStep S102), the blade operation control part 15 outputs a temporarycommand current corresponding to “lift-fixed” and finishes theprocessing. The temporary command current is input to the blade controlrestricting part 20. “Lift fixed” corresponds to refraining fromconducting the raising and lowering operation of the blade 4.

In a case where the condition of Step S102 is not satisfied (NO in StepS102), the blade operation control part 15 outputs a temporary commandcurrent corresponding to “lift-down” and finishes the processing. Thetemporary command current is input to the blade control restricting part20. “Lift-down” corresponds to operation for lowering the blade 4.

The flow shown in FIG. 4 represents processing intended to maintain ablade load f during the digging work within a range between the firstload threshold value f1 and the second load threshold value f2. In theflow, when the blade load f is equal to or greater than the second loadthreshold value f2, a load exceeding a digging capacity of the blade 4is considered to be applied to the blade 4, and “lift-up” operation isconducted for lessening the blade load f. When the blade load f issmaller than the first load threshold value f1, a load applied to theblade 4 is considered excessively small for the digging capacity, sothat “lift-down” operation is conducted for increasing a digging amount.Otherwise, processing of fixing a position of the, blade 4, i.e.,processing of refraining from conducting the raising and loweringoperation of the blade 4 is conducted.

Next, in Step S6 shown in FIG. 3, the controller 10 determines whether acondition that the temporary command current output by the bladeoperation control part 15 corresponds to “lift-up” is satisfied or not(Step S6). In a case where the condition is satisfied (YES in Step S6),the blade control restricting part 20 conducts processing of Step S11.In a case where the condition is not satisfied (NO in Step S6), a seriesof processing of subsequent Steps S7 to S11 is conducted.

The vehicle body position acquiring part 31 acquires the vehicle bodyposition, the vehicle body angle acquiring part 32 acquires the vehiclebody angle, and the blade angle acquiring part 33 acquires the angle ofthe blade 4 (Step S7). The blade position calculating part 12 calculatesthe blade position on the basis of the vehicle body position, thevehicle body angle, and the angle of the blade 4 (Step S8).

Next, the virtual design surface setting part 14 sets a virtual designsurface (Step S9). FIG. 5 is a diagram showing a flow for setting avirtual design surface by the virtual design surface setting part 14 ofthe controller 10. First, the virtual design surface setting part 14determines whether a condition corresponding to non-setting of a virtualdesign surface is satisfied or not (Step S201). In the specific exampleshown in FIG. 5, the virtual design surface setting part 14 determinesin Step S201 whether the Step S201 is the first time in the automaticcontrol or not. In a case where the Step S201 is the first time in theautomatic control, inevitably, a virtual design surface is not set, sothat the determination whether the step is the first time in theautomatic control or not can be determination whether a conditioncorresponding to non-setting of a virtual design surface is satisfied ornot. The determination whether the condition corresponding tonon-setting of a virtual design surface is satisfied or not may be alsomade on the basis of, for example, a flag (setting flag) indicative ofsetting or non-setting of a virtual setting surface.

In a case of determining that the Step is the first time in theautomatic control (YES in Step S201), the virtual design surface settingpart 14 newly sets a virtual design surface and finishes the processing.In a case of determining that the Step is not the first time in theautomatic control (NO in Step S201), the virtual design surface settingpart 14 determines whether a condition is satisfied or not, thecondition being that a blade load f acquired last time by the blade loadacquiring part 34 is equal to or greater than the first load thresholdvalue f1 and a blade load f acquired this time by the blade loadacquiring part 34 is smaller than the first load threshold value f1(Step S202). In a case where the condition in question is satisfied (YESin Step S202), the virtual design surface setting part 14 newly sets avirtual design surface (update the virtual design surface) and finishesthe processing.

In a case where the condition of Step S202 is not satisfied (NO in StepS202), determination is made whether a condition that the estimatedposition is below the virtual design surface is satisfied or not (StepS203). In a case of determining that the condition of Step 5203 issatisfied (YES in Step S203), the virtual design surface setting part 14newly sets a virtual design surface (update the virtual design surface)and finishes the processing. In a case where the condition of Step S203is not satisfied (NO in Step S203), the virtual design surface settingpart 14 refrains from updating the virtual design surface and finishesthe processing.

The flow shown in FIG. 5 represents processing intended to appropriatelyset a virtual design surface SV. In the flow, processing of newlysetting the virtual design surface SV (processing of updating thevirtual design surface SV) is conducted in a case where at least one ofthe conditions is satisfied, the conditions including the condition that“the step is the first time in the automatic control” (Step S201), thecondition that “a blade load f acquired last time is equal to or greaterthan the first load threshold value f1 and a blade load f acquired thistime is smaller than the first load threshold value f1” (Step S202), andthe condition that “the estimated position is below the currently setvirtual design surface SV” (Step S203). Execution of the processing inquestion causes the virtual design surface SV to be set at anappropriate time to realize stable digging work with high work executionefficiency.

FIG. 6 is a schematic side view for explaining the estimated position.An estimated position PB shown in FIG. 6 is calculated by the estimatedposition calculating part 22. Because of being arranged in a lowerportion of the work machine, the blade 4 and the travelling device 2 arepositioned at a height close to a height position of a present surfaceSP. Accordingly, at least one of the blade 4 and the travelling device 2can be an index for determining a positional relationship between thevirtual design surface SV and the present surface SP. The estimatedposition PB calculated by the estimated position calculating part 22 isobtained by calculating and estimating a part of the present surface SP,the part being associated with at least one of the blade 4 and thetravelling device 2, by the estimated position calculating part 22 onthe basis of the position information. Accordingly, when the conditionthat the estimated position PB is below the virtual design surface SV issatisfied, a possibility that the blade 4 enters a state of floatingabove the present surface SP will be increased. Since when the updatecondition including this condition is satisfied, the virtual designsurface SV is updated to have an angle parallel to the vehicle bodyangle with the blade position as a reference, the state where the blade4 floats above the present surface SP is eliminated.

In the present embodiment, the estimated position PB is an intersectionpoint between a line (line on the present surface SP in FIG. 6) parallelto a lower portion of the travelling device 2 in the work machine and aline L passing the blade position and extending perpendicularly from thevirtual design surface SV as shown in FIG. 6. Since the estimatedposition PB is an estimated height position of the present surface SP atthe blade position, the estimated position can be a point ofintersection, for example, at which the line parallel to the lowerportion of the travelling device 2 in the work machine and the blade 4intersect with each other.

FIG. 7 is a schematic side view for explaining a method of setting thevirtual design surface SV in the blade control device 100. In thepresent embodiment, in a case where the update condition is satisfied,the virtual design surface setting part 14 calculates a referenceposition, on a straight line passing the blade position andperpendicular to the target design surface SD, below the blade positionby a reference distance 6 set in advance, and sets, as the virtualdesign surface SV, a plane passing the reference position and parallelto the vehicle body angle as shown in FIG. 7.

Next, the blade control restricting part 20 calculates a command currentin Step S10 shown in FIG. 3. FIG. 8 is a diagram showing a flow forcalculating the command current by the blade control restricting part 20of the controller 10. As shown in FIG. 8, the blade control restrictingpart 20 determines whether a condition is satisfied or not, thecondition being that a blade position calculated by the blade positioncalculating part 12 is below the virtual design surface SV (Step S301).In a case where the condition in question is satisfied (YES in StepS301), the blade control restricting part 20 sets the command current tocorrespond to “lift-up” and finishes the processing . “Lift-up”corresponds to operation of raising the blade 4. On the other hand, in acase where the condition is not satisfied (NO in Step S301), the bladecontrol restricting part 20 sets the command current to be the same asthe temporary command current input from the blade operation controlpart 15 and finishes the processing.

The flow shown in FIG. 8 is processing intended to maintain the bladeposition above the virtual design surface SV. For example, even when acalculation result obtained by the blade operation control part 15corresponds to “lift-down” or “lift-fixed” (i.e., even when the bladeload f is small for the digging capacity of the blade 4), in a casewhere the blade control restricting part 20 determines that the bladeposition is below the virtual design surface SV, processing is conductedfor overwriting the command current with “lift-up” such that the bladeposition does not fall below the virtual design surface SV. Thisprevents generation of waviness on an execution surface SC.

In Step S11 shown in FIG. 3, the blade control restricting part 20outputs the command current to the lift cylinder control proportionalvalve 41. Specifically, in a case where a condition that the temporarycommand current output by the blade operation control part 15corresponds to “lift-up” is satisfied (YES in Step S6), the bladecontrol restricting part 20 outputs the same command current as thetemporary command current to the proportional valve 41. Additionally, ina case of NO in the Step S6, the blade control restricting part 20outputs a command current calculated in Step S10 to the proportionalvalve 41. When the processing of Step S11 is finished, the controller 10again conducts the processing of Step S1.

In the following, advantages of the blade control device 100 accordingto the above-described present embodiment will be specifically describedin comparison with a blade control device according to a referenceexample.

FIG. 15 is a schematic side view showing one example of a design surfaceSD (target design surface), present surfaces SP1 and SP2, virtual designsurfaces SV11, SV12, SV13, and SV21, and execution surfaces SC1 and SC2when a work machine provided with the blade control device according tothe reference example conducts digging work while ascending a slopealong the present surfaces SP1 and SP2.

In the reference example shown in FIG. 15, since the virtual designsurface SV11 is parallel to the design surface SD, a distance betweenthe present surface SP1 and the virtual design surface SV11 is increasedtoward an upper part of the upward slope. Accordingly, as shown in theupper view of FIG. 15, as the work machine ascends the slope along thepresent surface SP1 while digging the present surface SP1, a blade loadwill be remarkably increased. Then, when the blade load becomes greaterthan a predetermined second threshold value, the blade operation controlpart raises a blade 104, so that the blade load will he graduallydecreased. When the blade load becomes smaller than a predeterminedfirst threshold value (a value smaller than the second threshold value),the virtual design surface setting part updates the virtual designsurface SV11 to the virtual design surface SV12. The updated virtualdesign surface SV12 is set to be parallel to the horizontal designsurface SD and is set to be above the virtual design surface SV11 setlast time. While first digging work is thus conducted in which the workmachine ascends the slope along the present surface SP1 to dig the wholeof the present surface SP1, the plurality of horizontal virtual designsurfaces SV11, SV12, and SV13 is set in a stepped manner as shown in theupper view of FIG. 15, and the execution surface SC1 executed by thefirst digging work is also formed to be stepped. Thus formed steppedfirst execution surface SC1 will make the present surface SP2 as anobject to be dug in second digging work to be conducted next (see alower view of FIG. 15). Accordingly, as shown in the lower view of FIG.15, when the work machine ascends the slope along the present surfaceSP2 while digging the present surface SP2 in the second digging work,the vehicle body of the work machine greatly fluctuates in its pitchdirection. This will be a cause of reduction in controllability ofcontrolling a posture of the work machine and ride comfort of a worker.

FIG. 16 is a schematic side view showing one example of a design surfaceSD, a present surface SP, a virtual design surface SV11, and anexecution surface SC when the work machine provided with the bladecontrol device according to the reference example conducts the diggingwork while descending a slope along the present surface SP. The virtualdesign surface SV21 in the lower view of FIG. 15 is a virtual designsurface set for the second digging work and is a virtual design surfaceparallel to the target design surface SD.

In the reference example shown in FIG. 16, since the virtual designsurface SV11 is parallel to the design surface SD, a distance betweenthe present surface SP and the virtual design surface SV11 is decreasedtoward a lower part of the downward slope. Accordingly, as shown in anupper view of FIG. 16, when the work machine descends the slope alongthe present surface SP while digging the present surface SP, there isinevitably generated a region where the horizontal virtual designsurface SV11 goes above the present surface SP. In such a region wherethe horizontal virtual design surface SV11 goes above the presentsurface SP, the blade 104 restricted to fluctuate above the virtualdesign surface SV11 will inevitably float above the present surface SP,which prevents digging of the present surface SP as shown in a middleview of FIG. 16 and a lower view of FIG. 16. Besides, since a virtualdesign surface to be updated when a blade load becomes smaller than thefirst threshold value is set further above the virtual design surfaceSV11 of the last time, the blade 104 will float further above thepresent surface SP. This will be a cause of reduction in work executionefficiency.

On the other hand, since in the blade control device 100 according tothe present embodiment, the virtual design surface SV set by the virtualdesign surface setting part 14 is not parallel to the target designsurface SD but parallel to the vehicle body angle, waviness of theexecution surface SC can be suppressed and controllability of a postureof the work machine, ride comfort of a worker, and work executionefficiency during the digging work can be also suppressed. Specifics areas follows.

FIG. 9 is a schematic side view showing one example of a design surfaceSD (target design surface), a present surface SP, a virtual designsurface SV, and an execution surface SC when the work machine providedwith the blade control device 100 according to the present embodimentconducts the digging work while ascending a slope along the presentsurface SP, and FIG. 10 is a schematic side view showing one example inwhich the work machine conducts the digging work while descending aslope along the present surface SP. FIG. 11 is a schematic side viewshowing one example in which the work machine conducts the digging workwhile ascending and descending a slope along a present surface SP.

As shown in FIG. 9, since in the present embodiment, the virtual designsurface SV is set in parallel to the vehicle body angle of the workmachine ascending the slope along the present surface SP of theup-grade, the virtual design surface SV will not be set in a steppedmanner as in the reference example shown in the upper view of FIG. 15,resulting in suppressing also the execution surface SC from being formedin a stepped manner. This suppresses fluctuation of the vehicle body ina pitch direction at the time of again digging the execution surface SC,thereby obtaining an effect of eliminating deterioration incontrollability of a posture of the work machine and deterioration inride comfort of a worker.

Additionally, setting the virtual design surface SV to be parallel tothe vehicle body angle of the work machine descending the slope alongthe present surface SP of the down-grade as shown in FIG. 10 enablesresetting of the virtual design surface SV (the virtual design surfaceSV of the down-grade) parallel to the vehicle body angle of the workmachine having a posture along the present surface SP of the down-grade.This enables, even if the virtual design surface SV enters a state ofbeing above the present surface SP, elimination of the state to therebysuppress reduction in work execution efficiency.

Further, the blade control device 100 according to the presentembodiment is effective also in a case where the present surface has arelatively large uneven spot as shown in FIG. 11. In the presentembodiment, the virtual design surface SV can have various anglesaccording the vehicle body angle. As shown in FIG. 11, this suppresses aplurality of virtual design surfaces SV1, SV2, SV3, and SV4 from beingformed in a horizontal stepped manner as in the reference example, thevirtual design surfaces being set during the first digging work in whichthe work machine ascends the slope along the present surface SP to digthe whole of the present surface. In other words, since each of theplurality of virtual design surfaces SV1, SV2, SV3, and SV4 formed inthe first digging work is set in parallel to the vehicle body angle ofthe work machine having a posture along the present surface SP of theup-grade, the plurality of virtual design surfaces SV is liable tofollow the up-grade of the present surface SP. This suppresses steppedformation of the execution surface SC which is to be formed in the firstdigging work by the blade 4 having raising and lowering operationrestricted on the basis of the virtual design surfaces SV1, SV2, SV3,and SV4, so that the execution surface SC is liable to be less uneven ascompared with the reference example. Accordingly, when in the seconddigging work in which the execution surface SC of the first digging workis used as a present surface, the work machine ascends the slope alongthe present surface while digging the present surface, fluctuation ofthe vehicle body of the work machine in its pitch direction can besuppressed. This suppresses deterioration in controllability ofcontrolling a posture of the work machine and deterioration in ridecomfort of a worker. Additionally, waviness of such an execution surfacedug by the blade 4 as described above will be suppressed, the bladehaving raising and lowering operation restricted on the basis of thevirtual design surfaces SV1, SV2, SV3, and SV4.

Modification Example

FIG. 12 is a block diagram showing a main function of a blade controldevice 100 according to a modification example of the presentembodiment. FIG. 13 is a flowchart showing one example of controloperation to be executed by a controller 10 included in the bladecontrol device 100 according to the modification example. FIG. 14 is aschematic side view showing one example of a design surface SD, apresent surface SP, a virtual design surface SV, and an executionsurface SC when a work machine provided with the blade control device100 according to the modification example conducts digging work whileascending and descending a slope along the present surface SP.

The blade control device 100 according to the modification example shownin FIG. 12 is different from the blade control device 100 shown in FIG.2 in that the controller 10 further includes a vehicle body averageangle calculating part 21, and has the remaining configuration being thesame as that of the blade control device 100 shown in FIG. 2.Additionally, the flowchart shown in FIG. 13 is different from theflowchart shown in FIG. 3 in that between the processing of Step S8 andthe processing of Step S9, processing of Step S12 is added, and includesthe remaining processing being the same as that of the flowchart shownin FIG. 3.

The vehicle body average angle calculating part 21 calculates an averagevalue of vehicle body angles acquired by the position informationacquiring part. In the modification example, the virtual design surfacesetting part 14 is configured to use the average value of the vehiclebody angles as the vehicle body angle to be a reference for setting thevirtual design surface SV.

Since in this modification example, even in a case where the presentsurface SP as an object to be dug has a relatively large uneven spot,the virtual design surfaces SV1, SV2, SV3, and SV4 are set to beparallel to an average value of the vehicle body angles as shown in FIG.14, update time of the virtual design surfaces SV2, SV3, and SV4 is lessliable to depend on a local uneven spot and the like. This enablesreduction in an amount of change in angles of the virtual designsurfaces SV2, SV3, and SV4 at the time of update to thereby enable morestable digging work.

Although it is possible to adopt, as the average value of the vehiclebody angles, for example, a moving average value of a plurality ofvehicle body angles acquired by the vehicle body angle acquiring part 32between time when the virtual design surface SV is updated and timebefore the update time by a predetermined time period, an average valuecalculation method is not limited to the above-described method.

In this modification example, in a case where the update condition issatisfied, the virtual design surface setting part 14 calculates areference position, on a straight line passing the blade position andperpendicular to the target design surface SD, below the blade positionby a reference distance S set in advance, and sets, as the virtualdesign surface SV, a plane passing the reference position and parallelto the average value of the vehicle body angles. In other words, in thismodification example, a plane parallel to the average value of thevehicle body angles in continuous time is set as a virtual designsurface, and this arrangement allows the virtual design surface SV tofollow an average angle of the vehicle body, i.e., follow an averagegradient of the present surface even in a case where the present surfacehas an uneven spot. This enables reduction in an amount of change in anangle of the virtual design surface at the time of update to therebyenable more stable digging work.

As a specific example, since in the modification example shown in FIG.14, the virtual design surface SV is set to be parallel to the averagevalue of the vehicle body angles in continuous time, an amount of changein an angle of the virtual design surface at the time of update can bereduced, resulting in having an effect of eliminating deterioration ofwork execution efficiency and an effect of enabling more stable diggingas compared with the embodiment shown in FIG. 11.

The present invention is not limited to the above-described embodiments.The present invention may include the following modes, for example.

A work machine to which the blade control device according to thepresent invention is applied is not limited to a hydraulic excavator.The present invention is widely applicable to other work machineprovided with a blade, such as a wheel loader, a bulldozer, and thelike.

As described in the foregoing, there is provided a blade control devicecapable of effectively suppressing waviness of an execution surface.

The blade control device is a device which is provided in a work machineincluding a machine body having a travelling device and a vehicle bodysupported by the travelling device and a blade attached to the machinebody so as to be raised and lowered and which controls raising andlowering operation of the blade. The blade control device includes atarget design surface setting part which sets a target design surfacethat specifies a target shape of an object to be dug by the blade; aposition information acquiring part which acquires position informationrelated to the work machine; a blade position calculating part whichcalculates a blade position as a position of the blade on the basis ofthe position information acquired by the position information acquiringpart; a virtual design surface setting part which sets a virtual designsurface above the target design surface; and a blade operation controlpart which controls the raising and lowering operation of the blade. Ina case where an update condition set in advance is satisfied, thevirtual design surface setting part sets the virtual design surface,using the blade position when the update condition is satisfied as areference, at an angle equivalent to a vehicle body angle as an angle ofinclination of the vehicle body with respect to a horizontal surface,the angle of inclination being obtained on the basis of the positioninformation. The blade operation control part restricts the raising andlowering operation of the blade such that the blade conducts the raisingand lowering operation above the virtual design surface.

In the blade control device, the virtual design surface is set not to beparallel to the target design surface but to be parallel to the vehiclebody angle. Accordingly, in a case, for example, where a present surface(the ground) has an up-grade or a down-grade with respect to ahorizontal target design surface and a work machine conducts diggingwork while ascending a slope along the present surface or descending theslope along the present surface, the virtual design surface is liable tofollow the up-grade or the down-grade. This suppresses fluctuation of adistance between the present surface and the virtual design surface,thereby suppressing fluctuation of a blade load as well. Whenfluctuation of a blade load is suppressed, the raising and loweringoperation of the blade will be suppressed, so that waviness of anexecution surface will be suppressed.

Preferably, the blade control device further includes an estimatedposition calculating part which calculates an estimated position of apart of a present surface which is the ground as the object to be dug,the part being associated with at least one of the blade and thetravelling device, on the basis of the position information acquired bythe position information acquiring part, in which the update conditionincludes a condition that the estimated position is below the virtualdesign surface.

In a case where a present surface (the ground) as an object to be dughas a relatively large uneven spot, a vehicle body angle of the workmachine relatively greatly fluctuates, and a virtual design surface setin parallel to the vehicle body angle is liable to be set in arelatively large angle range. In such a case, there occurs a case whereduring the digging work, the virtual design surface may be temporarilypositioned above a part, of the present surface, corresponding to theblade, or a part, of the present surface, corresponding to thetravelling device. As a result, the blade restricted to be above thevirtual design surface enters a state of floating above the presentsurface. When such a state continues long, efficiency of the diggingwork is deteriorated. Here, because of being arranged in a lower portionof the work machine, the blade and the travelling device are positionedat a height close to a height position of a present surface.Accordingly, at least one of the blade and the travelling device can bean index for determining a positional relationship between the virtualdesign surface and the present surface. In the present mode, theestimated position calculated by the estimated position calculating partis obtained by calculating and estimating a part of the present surface,the part being associated with at least one of the blade and thetravelling device, by the estimated position calculating part on thebasis of the position information. Accordingly, when the condition thatthe estimated position is below the virtual design surface is satisfied,a possibility that the blade enters a state of floating above thepresent surface will be increased. Since in the present mode, when theupdate condition including this condition is satisfied, the virtualdesign surface is updated to have an angle parallel to the vehicle bodyangle with the blade position as a reference, the state where the bladefloats above the present surface is eliminated.

In the blade control device, the update condition preferably includes acondition corresponding to non-setting of the virtual design surface. Ina case, for example, where at the start of automatic control of theblade, a virtual design surface is not set, when the update conditionincluding the condition in question is satisfied, a virtual designsurface parallel to a vehicle body angle is set. This enables diggingwork to have high work execution efficiency from an initial stage of theautomatic control of the blade.

Preferably, the blade control device further includes a blade loadacquiring part which acquires a blade load as a load applied to theblade; and a storage part which stores a load threshold value as athreshold value of the blade load, in which the update conditionincludes a condition that the blade load changes from a value equal toor greater than the load threshold value to a value smaller than theload threshold value.

Time when the blade load changes from a value equal to or greater thanthe load threshold value to a value smaller than the load thresholdvalue, in many cases, corresponds to time when operation of reducing aload applied to the blade is conducted. Such a state of a reduced bladeload is a more desirable state as compared with a state of an increasedblade load in view of stability of the digging work. Accordingly,stability of the digging work is improved by setting, when the updatecondition including the condition in question is satisfied, a virtualdesign surface, and conducting the digging work in which the raising andlowering operation of the blade is restricted on the basis of thevirtual design surface.

The blade control device is preferably configured to further include avehicle body average angle calculating part which calculates an averagevalue of vehicle body angles acquired by the position informationacquiring part, in which the virtual design surface setting part usesthe average value of the vehicle body angles as the vehicle body angleto be a reference for setting the virtual design surface. Since in thismode, even in a case where a present surface as an object to be dug hasa relatively large uneven spot, a virtual design surface is set to beparallel to the average value of the vehicle body angles, update time ofthe virtual design surface is less liable to depend on a local unevenspot and the like. This enables reduction in an amount of change in anangle of the virtual design surface at the time of update to therebyenable more stable digging work.

1. A blade control device which is provided in a work machine includinga machine body having a travelling device and a vehicle body supportedby the travelling device and a blade attached to the machine body so asto be raised and lowered and which controls raising and loweringoperation of the blade, the blade control device comprising: a targetdesign surface setting part which sets a target design surface thatspecifies a target shape of an object to be dug by the blade; a positioninformation acquiring part which acquires position information relatedto the work machine; a blade position calculating part which calculatesa blade position as a position of the blade on the basis of the positioninformation acquired by the position information acquiring part; avirtual design surface setting part which sets a virtual design surfaceabove the target design surface; and a blade operation control partwhich controls the raising and lowering operation of the blade, whereinin a case where an update condition set in advance is satisfied, thevirtual design surface setting part sets the virtual design surface,using the blade position when the update condition is satisfied as areference, at an angle equivalent to a vehicle body angle as an angle ofinclination of the vehicle body with respect to a horizontal surface,the angle of inclination being obtained on the basis of the positioninformation, and the blade operation control part restricts the raisingand lowering operation of the blade such that the blade conducts theraising and lowering operation above the virtual design surface.
 2. Theblade control device according to claim 1, further comprising anestimated position calculating part which calculates an estimatedposition of a part of a present surface which is the ground as theobject to be dug, the part being associated with at least one of theblade and the travelling device, on the basis of the positioninformation acquired by the position information acquiring part, whereinthe update condition includes a condition that the estimated position isbelow the virtual design surface.
 3. The blade control device accordingto claim 1, wherein the update condition includes a conditioncorresponding to non-setting of the virtual design surface.
 4. The bladecontrol device according to claim 1, further comprising: a blade loadacquiring part which acquires a blade load as a load applied to theblade; and a storage part which stores a load threshold value as athreshold value of the blade load, wherein the update condition includesa condition that the blade load changes from a value equal to or greaterthan the load threshold value to a value smaller than the load thresholdvalue.
 5. The blade control device according to claim 1, furthercomprising a vehicle body average angle calculating part whichcalculates an average value of vehicle body angles acquired by theposition information acquiring part, wherein the virtual design surfacesetting part uses the average value of the vehicle body angles as thevehicle body angle to be a reference for setting the virtual designsurface.